He stopped whistling for a moment, but then started again as soon as the other people had left the room. = 'Hän lakkasi viheltämästä ~ lopetti viheltämisen hetkeksi, mutta aloitti heti uudestaan muiden lähdettyä huoneesta.'

Thanks, DrW. For whatever reason, the WSOY dictionary gives pysähytyä, pitää tauko or tauota as translations of the verb "pause" (= to temporarily stop), but doesn't mention lakata or lopettaa, so I wasn't sure if they could be used in the first sentence.